[marcatio]

ATLksuGUY,

There shouldn't be any problem with bonding the two different types of concrete, as essentially concrete is comprised of three main components, water, portland cement, and aggregates (crushed stone, washed gravel). The differences in the concrete mix designs come from the water/cement ratio, types of aggregates, and admixtures (additives added to give concrete different qualities).

Concrete that is exposed to weather is air-entrained concrete, that is concrete that has tiny air bubbles within which allow moisture within to expand when it freezes.

When two pours are made at different times, several methods are used to insure bonding. Sometimes an epoxy is painted on the previously poured concrete, or the surface of the previous pour is roughened to allow bonding.